What will be basic advantage of having both systems simultaneously?
You are touching on a sensitive subject. Not just for technical considerations, but emotional.
Like it or not, a rising deck, aka 'ramp', method to launch an aircraft is a sign of inferior technical and financial factors. Not everyone is going to like it and that is why I said 'emotional'. Nobody like to hear his country is 'inferior' in anyway.
A 'ski jump' ramp is a technical and financial compromise to the superiority of the catapult method. The ramp is not as simple to design and constructed as its appearance seems to imply. In fact, the ramp method is nearly as technically complex to design as the catapult. What the ramp does is to give the aircraft an external assist in
INITIAL pitch up attitude, as in getting as much air to the aircraft's underside as possible, which equal to rate of climb. However, at some point
AFTER leaving the ship, the aircraft's own thrust (as in thrust to weight ratio) must be sufficient to sustain what the ramp gave.
The ramp's rise is the result of complex calculations that takes into consideration ship's available deck length, which is not true (total) deck length, apportioned deck length for ramp operation, and types of aircrafts that can be assisted by the ramp. The
HMS Invincible ramp is seven degrees while other Royal Navy carriers have different rise angles.
HMS Ark Royal (R07)
HMS Ark Royal (R07), the last Invincible-class light aircraft carrier to be completed, is the fifth ship of the Royal Navy named in honour of the flagship of the English fleet that defeated the Spanish Armada. Ark Royal is slightly larger than her sister ships and during construction she was fitted with a steeper ski-jump ramp, (twelve degrees, as opposed to seven degrees of the Invincible) to improve STOVL take-off performance for the Harrier aircraft.
The disadvantages for the ramp method are many...
- Longer apportioned deck length for launch.
- Limited types of aircrafts that can be launched. For many aircrafts, such as cargo or heavy strike fighters, the launch may require most of available deck length, not just merely apportioned deck length.
- Limited weather operations than catapult. The ramp's rise blocks a considerable amount of usable moving air that could assist the aircraft. Whereas with the catapult, the aircraft is effectively secured to the deck and literally dragged to launch, making the catapult more flexible.
- Decreased aircraft weight for launch.
- Decreased tempo of air operations.
For the last but very important item -- tempo -- just in case you do not know the definition of the word, and not trying to be snarky...
tempo:
...the rate or speed of motion or activity; pace.
Because the ramp method require longer deck length to launch than the catapult, and because the deck already have limited real estate, to safely launch/recover aircrafts, the rate -- tempo -- of those operations must be even more regulated, meaning less margins of error, than the catapult method. And when there is an emergency, those activities will be even more restricted since the in-flight emergency (IFE) aircraft is an unknown variable in those deck operations because you do not know how much deck length does an IFE need to land and how much lateral room he needs to maneuver once he landed. You have to consider the possibility of the worst -- a crash -- so you want to have as little potential for collateral damages as possible.
But the worst disadvantage of the ramp came from the sum of all of the above: The ramp have a much greater effect on the quantity of
NATIVE aircraft the ship can deploy, as in negative effect.
The word 'native' is important. It mean the
TYPES of aircrafts that are permanently assigned to the ship. If you know, base on first yr university math, that you can only launch so-and-so rate of aircrafts for so-and-so types of missions those aircrafts are designed/designated to do, because of the ramp's limitations, it make no sense for you to deploy with excess, even including combat loss replacements. The Liaoning is reportedly capable of total at best 40 aircrafts of fixed and rotary types. The USS George HW Bush can carry 90 of both types. Size does matter but the catapult was a major factor in that quantity.
But despite the obvious technical and operational disadvantages of the ramp method, countries that dare to break into naval aviation uses it because they do not have the financial resources to create and sustain long term the technical expertise, in manpower and machineries, of the catapult method. Every single navy in the world have the potential to use all catapults, should they chose to make the leap into naval aviation, but not even the Soviet Navy during the peak of the Cold War, could afford the catapult method. Remember, the Liaoning was from the Russians.
